The present invention relates generally to a drive mechanism and more specifically to a drive mechanism for providing automatic torque amplification under high loading.
A gear or pulley arrangement is commonly used to transmit drive from an input shaft to an output shaft connected to a load. Often the load can vary considerably, altering torque requirements to drive the output shaft. In many applications, high torque may only be necessary a relatively short period of time to overcome a temporary overload condition. For example, when the driven shaft is connected to the unloading chain of an implement such as a stack wagon for hay, the starting torque necessary to begin the load moving is much higher than that required to convey the load out once it begins to move.
Transmissions are available which shift automatically to vary the relationship between the input and output shaft speed such as shown in U.S. Pat. No. 3,436,977, but these are generally responsive to engine or shaft speed and require a relatively complex centrifugal or roller clutch which is difficult and expensive to manufacture. Other transmission devices similar to that shown in U.S. Pat. No. 1,143,048 are less complex but do not shift automatically.